I have 2007 XL 4.2 V6 5 speed manual. My question is what could possibly cause the rattle under acceleration coming more from the engine area. I've already checked the heat shields and what not. It seems to be more noticeable at highway speed when I'm giving it more gas.

 

Could be timing chain slapping possibly.

Heres what mine was doing before i redid tensioners, cam phasers, and chain guides (which were shattered into like 5 peices)


Heres after

 

Check all of your pulleys and their bearings also.
It could be preignition though. I think the 4.2's have an issue with that. Try running higher octane. If it goes away, then you probably have carbon built up in the cylinder. The carbon gets so hot that it ignites the fuel/air mixture before the sparkplug.

 

I will finish running out this tank and give that a try for sure. Thanks for the info

 

Well after some octane booster and a tank of 93 all is well with the rattle I will start using 89 on a regular basis now